This invention relates to collapsible self-supporting structures, and more particularly to a hub assembly for pivotally holding the ends of the column-like support rods which make up the skeletal frames for such collapsible structures.
The collapsible structures have network support rods which are pivotally joined together for movement between a collapsed, compact position for storage or transportation and an opened condition in which the desired structural shape is attained. Dome or arch shape structures of this type may be illustrated by U.S. Pat. Nos. 3,838,703, 3,968,808, 4,026,313, and 4,290,244. Collapsible display frame structures of the type having planar or arcuate face surfaces may be illustrated by U.S. Pat. Nos. 4,276,726 and 4,471,548. Such display frames are commercially available and are useful in setting up for trade show displays and the like.
The above-mentioned patents show various hub assembly structures for pivotally holding the ends of the support rods. Also, U.S. Pat. No. 4,280,521 specifically shows a multiple-bodied hub to be fused together to capture a ring and interconnected blades which extend from the support rod ends. These hub assemblies are characterized by having multiple parts that are typically designed to be permanently assembled together.
Because of the complex nature of the network of support rods, the hub assemblies must accommodate complex movements between the collapsible structure's opened and collapsed positions. Some twisting, flexing, and straining between the hub assemblies and support rods are inherent in such structures. Additionally, with repeated opening and collapsing of the structures typically used for trade show displays, the hub assemblies are subject to wear and may break rendering the entire collapsible structure useless. Replacement or repair of a hub assembly or a support rod may be impossible or difficult in addition to being time consuming. Therefore, such replacement or repair has generally been considered not feasible for many of the aforementioned structures.